On Wed, 13 Feb 2008, Jiri Kosina wrote:
> From: Jiri Kosina <[EMAIL PROTECTED]>
>
> loop - fix deadlock against block
>
> A: B:
> bdev_open() for ino X
> (locks bd_mutex for bdev Y)
> lo_ioctl(LOOP_CLR_FD) for ino X
> (locks lo_ctl_mutex)
> fput()
> __fput()
> blkdev_close()
> (hangs on bd_mutex for bdev Y)
> lo_open()
> (hangs on lo_ctl_mutex)
>
> Fix this by letting releasing the lock inside loop_clr_fd() after the
> loopback structure has been completely deinitialized, but before calling
> final fput().
>
> Signed-off-by: Jiri Kosina <[EMAIL PROTECTED]>
OK, the previous one was buggy, could you please try this one instead?
diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 91ebb00..bfb2e90 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -881,6 +881,7 @@ static int loop_clr_fd(struct loop_device *lo, struct
block_device *bdev)
struct file *filp = lo->lo_backing_file;
gfp_t gfp = lo->old_gfp_mask;
+ mutex_lock(&lo->lo_ctl_mutex);
if (lo->lo_state != Lo_bound)
return -ENXIO;
@@ -916,6 +917,7 @@ static int loop_clr_fd(struct loop_device *lo, struct
block_device *bdev)
bd_set_size(bdev, 0);
mapping_set_gfp_mask(filp->f_mapping, gfp);
lo->lo_state = Lo_unbound;
+ mutex_unlock(&lo->lo_ctl_mutex);
fput(filp);
/* This is safe: open() is still holding a reference. */
module_put(THIS_MODULE);
@@ -1143,8 +1145,11 @@ static int lo_ioctl(struct inode * inode, struct file *
file,
err = loop_change_fd(lo, file, inode->i_bdev, arg);
break;
case LOOP_CLR_FD:
+ /* loop_clr_fd must do the locking itself, so that it
+ * doesn't deadlock with bdev */
+ mutex_unlock(&lo->lo_ctl_mutex);
err = loop_clr_fd(lo, inode->i_bdev);
- break;
+ goto out_unlocked;
case LOOP_SET_STATUS:
err = loop_set_status_old(lo, (struct loop_info __user *) arg);
break;
@@ -1161,6 +1166,7 @@ static int lo_ioctl(struct inode * inode, struct file *
file,
err = lo->ioctl ? lo->ioctl(lo, cmd, arg) : -EINVAL;
}
mutex_unlock(&lo->lo_ctl_mutex);
+out_unlocked:
return err;
}
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